Estimating distances between devices

Abstract

A mobile recording device comprises means for detecting an audio signal emitted by the first device and means for measuring a strength of the audio signal. A server or the mobile comprises means for using the measured signal strength to estimate a distance between the first and second devices. A server comprises means for storing first and second collections of data sets, each of the data sets of the first collection comprising an emission time stamp, each of the data sets of the second collection comprising a reception time stamp and data indicative of a received signal strength; means for using emission time stamps and reception time stamps of the data sets to identify a data set of the first collection that corresponds to a data set of the second collection; and means for using the data indicative of the signal strength from the identified data set of the second collection to estimate the distance between devices that are sources of the identified data sets.

1 - 68 . (canceled) 
     
     
         69 . A method of estimating a distance between a first device and a second device, the method comprising the second device:
 detecting an audio signal emitted by the first device;   measuring a strength of the audio signal; and   using the measured signal strength to estimate a distance between the first and second devices.   
     
     
         70 . The method of  claim 69 , wherein detecting an audio signal comprises detecting a sinusoidal audio signal emitted by the first device at a specific frequency. 
     
     
         71 . The method of  claim 70 , wherein detecting a sinusoidal audio signal comprises detecting using the Goertzel algorithm. 
     
     
         72 . The method of  claim 69 , wherein detecting an audio signal comprises detecting a tonal signal with a frequency that varies with time. 
     
     
         73 . The method of  claim 69 , wherein detecting an audio signal comprises detecting an audio signal with tonal content at plural frequencies. 
     
     
         74 . The method of  claim 69 , further comprising mapping distance to a textual location. 
     
     
         75 . The method of  claim 69 , comprising refraining from using the measured signal strength to estimate a distance between the first and second devices when signal strength is below a threshold signal strength. 
     
     
         76 . The method of  claim 69 , comprising using measured signal strength from signals transmitted in both directions between the first and second devices to estimate the distance between the devices. 
     
     
         77 . The method of  claim 76 , comprising using the highest measured signal strength from signals transmitted in both directions between the first and second devices to estimate the distance between the devices. 
     
     
         78 . A method as claimed in  claim 69 , wherein using the measured signal strength to estimate a distance between the first and second devices comprises:
 storing first and second collections of data sets, each of the data sets of the first collection comprising an emission time stamp, each of the data sets of the second collection comprising a reception time stamp and data indicative of the measured received signal strength;   using emission time stamps and reception time stamps of the data sets to identify a data set of the first collection that corresponds to a data set of the second collection; and   using the data indicative of the signal strength from the identified data set of the second collection to estimate the distance between the first and second devices.   
     
     
         79 . Apparatus, the apparatus having at least one processor and at least one memory having computer-readable code stored therein which when executed controls the at least one processor to:
 detect an audio signal emitted by the first device;   measure a strength of the audio signal; and   use the measured signal strength to estimate a distance between the first and second devices.   
     
     
         80 . Apparatus as claimed in  claim 79 , wherein the computer-readable code when executed controls the at least one processor to detect an audio signal, wherein the sinusoidal audio signal emitted by the first device is at a specific frequency. 
     
     
         81 . Apparatus as claimed in  claim 80 , wherein the computer-readable code when executed controls the at least one processor to detect a sinusoidal audio signal using the Goertzel algorithm. 
     
     
         82 . Apparatus as claimed in  claim 79 , wherein the computer-readable code when executed controls the at least one processor to detect an audio signal, wherein the audio signal is a tonal signal with a frequency that varies with time. 
     
     
         83 . Apparatus as claimed in  claim 79 , wherein the computer-readable code when executed controls the at least one processor to detect an audio signal, wherein the audio signal comprises tonal content at plural frequencies. 
     
     
         84 . Apparatus as claimed in  claim 79 , wherein the computer-readable code when executed controls the at least one processor to map distance to a textual location. 
     
     
         85 . Apparatus as claimed in  claim 79 , wherein the computer-readable code when executed controls the at least one processor to refrain from using the measured signal strength to estimate a distance between the first and second devices when signal strength is below a threshold signal strength. 
     
     
         86 . Apparatus as claimed in  claim 79 , wherein the computer-readable code when executed controls the at least one processor to use measured signal strength from signals transmitted in both directions between the first and second devices to estimate the distance between the devices. 
     
     
         87 . Apparatus as claimed in  claim 86 , wherein the computer-readable code when executed controls the at least one processor to use the highest measured signal strength from signals transmitted in both directions between the first and second devices to estimate the distance between the devices. 
     
     
         88 . Apparatus as claimed in  claim 79 , wherein the computer-readable code when executed controls the at least one processor to use the measured signal strength to estimate a distance between the first and second devices, further controls the at least one processor to:
 store first and second collections of data sets, each of the data sets of the first collection comprising an emission time stamp, each of the data sets of the second collection comprising a reception time stamp and data indicative of the measured received signal strength;   use emission time stamps and reception time stamps of the data sets to identify a data set of the first collection that corresponds to a data set of the second collection; and   use the data indicative of the signal strength from the identified data set of the second collection to estimate the distance between the first and second devices.   
     
     
         89 . A non-transitory computer-readable storage medium having stored thereon computer-readable code, which, when executed by computing apparatus, causes the computing apparatus to perform a method comprising:
 detecting an audio signal emitted by the first device;   measuring a strength of the audio signal; and   using the measured signal strength to estimate a distance between the first and second devices.   
     
     
         90 . A non-transitory computer-readable storage medium as claimed in  claim 89  wherein the computer-readable code when executed by computing apparatus causes the computing apparatus to detect an audio signal emitted by the first device at a specific frequency. 
     
     
         91 . A non-transitory computer-readable storage medium as claimed in  claim 90  wherein the computer-readable code when executed by computing apparatus causes the computing apparatus to detect a sinusoidal audio signal using the Goertzel algorithm.